These photos are of a sunset on Upper Kananaskis Lake in Kananaskis Country looking roughly northwest from the southeast shore. These were my first real shots using my new filters and I kind of botched both of them.

Thanks for the comment Dave. I am using Cokin. I believe for the magenta one I stacked 4 filters:
• 1 Cokin P164 Circular Polarizer
• 2 Cokin P154 3 stop Neutral Density Filters
• 1 Cokin P121S 3 stop soft Graduated Neutral Density Filter
That provided a total of about 11 2/3 stops at the top of the frame. That's a LOT of filtration. I tried all of those filters another time and found the color shift was greatly exaggerated this time. Perhaps it's a combination of the longer exposure time, and the mix of light. The real color was much more similar to the bottom blue picture to my eyes.
Overall I'm still pretty happy with the Cokin filters and only had a few other images which experienced color shift, generally stacking the CPL, ND8 and the GND8 while hiking to Ptarmigan Cirque, in those cases it's EASILY fixed in photo shop. I suspect it's not only greatly effected by the conditions but it might also be an exponential problem and the 2nd GND8 was the straw that broke the camel's back.